Hollow core doors simulating natural, solid doors are well known in the art. Such doors typically include a peripheral frame, with two door facings secured to opposing sides of the frame. The door facings may be formed from wood composite, such as hardboard, medium density fiberboard, oriented strandboard, wood plastic composites, and the like. The facings may have a smooth, planar surface, a textured surface and/or a contoured surface. Contoured, or molded, door facings are often formed to have portions simulating stiles, rails and panels, as found in traditional wooden rail and stile doors.
Typically, the door also includes a core, which fills the internal void formed between the two opposing facings. The core may be formed from corrugated pads, low density fiberboard, particleboard, foamed insulation, or some other materials. For example, an expanding insulating foam material may be applied through holes drilled through the peripheral frame to provide access to the internal void. The core provides rigidity and structural integrity to the door, as well as desired thermal and acoustic characteristics of the door. However, the use of a core increases manufacturing costs.
Door facings formed from sheet molding compound (SMC) with expensive glass fibers, or similar resin based materials, may be formed to have deep draw contoured portions, given the moldable characteristics of such materials. However, the moldability of wood composites requires consideration of certain factors and parameters different than those addressed for SMC materials. Typically, a wood composite panel is formed from a loose mat of very short cellulosic fibers or particles. The mat may be 2 inches thick or more prior to compression. The mat is then compressed to form the facing or panel. As the mat is compressed, the fibers do not flow. Rather, the fiber mat is stretched, particularly in contoured portions. Contoured portions having steep sidewalls or curves, or deep draw depths, may result in surface cracks or defects due to the stretching of the fiber mat during compression.